Progress in the treatment of persons with advanced HIV infection (HIV/AIDS) have transformed a rapidly fatal condition into a chronic debilitating disease that requires long-term ambulatory care. Minimal data are available on the response of the medical system to the huge demands which this epidemic has placed on ambulatory care providers. This project is designed to provide information on organizational components of ambulatory care for HIV/AIDS associated with improved patient outcomes. Ambulatory care patterns will be examined and classified for Medicaid-enrolled persons in New York State (NYS) with HIV/AIDS from 1986-1991. Our current AHCPR-funded AIDS project (end date: 9/92) has laid the foundation for this continuation study. The NYS Medicaid HIV/AIDS Research Data Base, developed in the parent project, contains longitudinal data on clinical diagnoses, treatments, service use, and expenditures for over 25,000 persons having evidence of AIDS from 1983-1990. The NYS HIV/AIDS Provider File, also produced in the parent project, contains physician and clinic-level data on HIV/AIDS experience, specialty, and location of practice. Significant findings from the parent project include: 1) 83 % of patients surviving > 6 months after AIDS diagnosis have clinic visits within the first 6 months of diagnosis; 2) the role of clinics as the dominant site, or primary provider, of ambulatory care increases dramatically from 54% before AIDS diagnosis to 79% after diagnosis, while the role of private physicians diminishes, from 46% to 21%; 3) the odds are greater that AIDS patients without a primary provider will present in emergency rooms (ERs) for care than will those with primary providers; and 4) persons having an AIDS specialty dominant provider or a consult with an AIDS specialist were more likely to receive AZT within 6 months of AIDS diagnosis than patients followed by other types of ambulatory care providers. In view of the central role that clinics serve in ambulatory care for individuals with HIV/AIDS, the following aims are proposed: 1) to expand the NYS Medicaid Provider Data Base through a survey of 250 clinic directors and classify organizational features of emerging models of ambulatory care for persons with advanced HIV disease; and 2) to determine if organizational characteristics of ambulatory care providers influence: a) hospital/ER use, b) use of specific drug therapies, and c) survival times of our patient population. Variations in patient outcomes will be analyzed by sex, age, drug use status, and year of diagnosis. This project will offer policymakers and clinicians broad-based assessment of the dominant ambulatory care models that have evolved for NYS Medicaid-enrollees with HIV/AIDS. These data can guide the development of systems of ambulatory care that are best prepared to meet the complex needs of persons with advanced HIV infection.